/*
 * Copyright 2012-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.web.servlet;

import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.ConstructorArgumentValues.ValueHolder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.ClassUtils;

/**
 * {@link ImportBeanDefinitionRegistrar} used by {@link ServletComponentScan}.
 *
 * @author Andy Wilkinson
 * @author Stephane Nicoll
 */
class ServletComponentScanRegistrar implements ImportBeanDefinitionRegistrar
{

    private static final String BEAN_NAME = "servletComponentRegisteringPostProcessor";

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry)
    {
        Set<String> packagesToScan = getPackagesToScan(importingClassMetadata);
        if (registry.containsBeanDefinition(BEAN_NAME))
        {
            updatePostProcessor(registry, packagesToScan);
        }
        else
        {
            addPostProcessor(registry, packagesToScan);
        }
    }

    private void updatePostProcessor(BeanDefinitionRegistry registry, Set<String> packagesToScan)
    {
        BeanDefinition definition = registry.getBeanDefinition(BEAN_NAME);
        ValueHolder constructorArguments = definition.getConstructorArgumentValues().getGenericArgumentValue(Set.class);
        @SuppressWarnings("unchecked")
        Set<String> mergedPackages = (Set<String>) constructorArguments.getValue();
        mergedPackages.addAll(packagesToScan);
        constructorArguments.setValue(mergedPackages);
    }

    private void addPostProcessor(BeanDefinitionRegistry registry, Set<String> packagesToScan)
    {
        GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
        beanDefinition.setBeanClass(ServletComponentRegisteringPostProcessor.class);
        beanDefinition.getConstructorArgumentValues().addGenericArgumentValue(packagesToScan);
        beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
        registry.registerBeanDefinition(BEAN_NAME, beanDefinition);
    }

    private Set<String> getPackagesToScan(AnnotationMetadata metadata)
    {
        AnnotationAttributes attributes =
                AnnotationAttributes.fromMap(metadata.getAnnotationAttributes(ServletComponentScan.class.getName()));
        String[] basePackages = attributes.getStringArray("basePackages");
        Class<?>[] basePackageClasses = attributes.getClassArray("basePackageClasses");
        Set<String> packagesToScan = new LinkedHashSet<String>();
        packagesToScan.addAll(Arrays.asList(basePackages));
        for (Class<?> basePackageClass : basePackageClasses)
        {
            packagesToScan.add(ClassUtils.getPackageName(basePackageClass));
        }
        if (packagesToScan.isEmpty())
        {
            return Collections.singleton(ClassUtils.getPackageName(metadata.getClassName()));
        }
        return packagesToScan;
    }

}
